Meloxicam (4-hydroxy-2-methyl-N-(5-methyl-2-thiazolyl)-2H-1,2-benzothiazine-3-carboxamide-1,1-dioxide) is an active substance which belongs to the group of NSAIDs (non-steroidal antiinflammatory drugs). Meloxicam and the sodium and meglumine (N-methyl-D-glucamine) salt thereof are described in EP-A-0 002 482. EP-A-0 002 482 shows, inter alia, the example of a 0.2% injectable solution of meloxicam consisting of the meglumine salt of the active substance, sodium chloride, and water.
EP-A-0 945 134 discloses the pH-dependent solubility characteristics of meloxicam and its salts, i.e., the sodium salt, the ammonium salt, and the meglumine salt, in aqueous solution. According to EP-A-0 945 134, meloxicam is an active substance which does not dissolve readily in water and the meloxicam salts, particularly the meglumine salt, exhibit improved solubility as the pH increases between 4 and 10, as shown in Table 1 of EP-0 945 134. However, until now it has only been possible to produce stable, clear, aqueous solutions with a low concentration of meloxicam. In addition to involving the in situ formation of a meloxicam salt, e.g., meglumine salt, and the addition of solubilizers, these prior art solutions were required to have a pH in the range of maximum possible solubility as well as being reasonably well-tolerated and contain a high proportion of organic solvent. Formulation tests with the same or a similar recipe led to cloudiness of the solution if the meloxicam concentrations were higher, e.g., 2%.
WO9959634 A1 describes an eye drop solution containing 0.5% meloxicam but makes no reference to possible meloxicam concentrations over 1%. For example, a commercially available 0.5% meloxicam solution is used in small animals such as dogs, heifers, and calves to treat respiratory diseases.
Thus, it has not hitherto been possible to treat large farm animals with an injectable meloxicam solution as the low concentration of active substance in the injectable solution did not allow an acceptable, well-tolerated injection volume due to the great weight of the animals. Furthermore, parenteral administration requires that the solution be free from particles; if there are particles in a parenteral drug, there is a risk of vascular damage or embolism. Moreover, organic solvents, solubilizers, and water-soluble substances can only be used in certain concentrations to achieve acceptable drug tolerance. These problems are solved by the present invention which provides particle-free, highly concentrated meloxicam solutions which are stable over long periods and suitable for treating farm animals up to 750 kg in weight. The meloxicam solutions of the present invention should, therefore, be suitable for administration both orally or parenterally.